18 March, 2017
"That's why we're excited to announce Guetzli, a new open source algorithm that creates high quality JPEG images with file sizes 35% smaller than now available methods, enabling webmasters to create webpages that can load faster and use even less data".More news: Tillerson's email alias was prompted by business needs, Exxon says
Google scientists have developed a new way to compress JPEG images which makes them 35% smaller than is possible using existing compression methods, the company has announced on its Research Blog. The smaller image sizes would help pages load faster, and could even allow users on a data plan to use less of their allocation loading images. Like Google's other web-centric compression algorithms, Guetzli doesn't change the base JPEG format so all current devices and browsers can view the generated images. The name Guetzli means cookie in Swiss German. Guetzli strikes a balance between minimal loss and file size by employing a search algorithm that tries to overcome the difference between the psychovisual modeling of JPEG's format, and Guetzli's psychovisual model, which approximates color perception and visual masking in a more thorough and detailed way than what is achievable by simpler color transforms and the discrete cosine transform. Per the example below, the uncompressed image is on the left, libjpeg-shrunk in the center and Guetzli-treated on the right. Google describes the slower compression process as a "worthy tradeoff". The advantage to using Guetzli instead of a new format is that the images are still regular JPEG files, and so they're still compatible with nearly every browser and application that exists. It would be interesting to see if Guetzli scores a wider acceptance. And although Google compared Guetzli to mozjpeg and another JPEG encoder called libjpeg, there are other options, too. For example, a multi-megabyte image stored in BMP or PNG format can look nearly exactly the same converted to a JPEG that's only a few hundred kilobytes in size. You can view Guetzli's repository on GitHub here. The company performed experiments where images of equal file size were shown to study participants who consistently prefered the imaged compressed using Guetzli. The team also suggests that the psychovisual approach adopted by the project will inspire further research into the way our eyes perceive compressed images and video.